Pressure controlled instrument



Nov. 3, 1942. F. H. HOPKINS 2,300,395

PRESSURE CONTROLLED INSTRUMENT Filed Dec. 22, 1941 5 Sheets-Sheet l a!"a?" 2 9 P 2; Wm M a p95 i 50 4 J Marla? F. H. HOPKINS PRESSURECONTROLLED INSTRUMENT Nov. 3, 1942.

22, 1941 3 Sheets-Sheet 2 Filed Dec.

Nov. 3, 1942. Q op s 2,300,895

PRESSURE CONTROLLED INSTRUMENT Filed Dec. 22, 1941 3 Sheets-Sheet I5Patented Nov. 3, 1942 PRESSURE CONTROLLED INSTRUMENT Frank H. Hopkins,Fairfleld, Conn., assignor to Manning, Maxwell & Moore. Incorporated,New York, N. Y., a corporation of New Jersey Application December 22,1941, Serial No. 423,942

9 Claims.

This invention relates to an improvement in a pressure controlledinstrument, and more particularly to an instrument of the type whichcomprises a snap switch and Bourdon tube, the latter acting upon theformer in response to variances in pressure, temperature or the like toopen or close an electrical circuit.

One purpose for such an instrument is to consystem within minimum andmaximum pressure limits, e. g., twenty and forty pounds, respectively.When the pressure in the system falls to the minimum limit (20 pounds),the Bourdon tube acts to close a switch by which a pump is actuated andholds the switch closed until the pressure in the line has reached tothe upper limit (40 pounds) at which time the switch is opened and thepump circuit broken.

The primary object of this invention is to regulate the operation of thesystem so that the switch contacts-are closed when a predeterminedminimum pressure is reached and are held closed until the predeterminedmaximum pressure is attained. This requires two controls, first, thatwhich determines the point at which the switch contacts are closed, andsecond, that which determines the length of the range of pressure orpressure diiferential during which the switch should remain closed.

More specifically in the illustrated embodiments which will be describedin detail hereinbelow, the first control is attained by initiallysetting the coacting switch and tube elements a predetermined distanceapart; the second control is attained by so designing the coactingelement of the Bourdon tube (hereinafter referred to as a finger) thatthe period of its effective coaction with the switch element may bealtered as desired to adjust the gap," i. e., the period during whichthe switch contacts remain closed.

These and other objects of the invention will be apparent from anexamination of the following description of several embodiments of theinvention and of the accompanying drawings which illustrate suchembodiments and in which Fig. l is a face view of an instrumentembodying one form of this invention, the cover thereof having beenremoved and the switch being shown in section with the switch open;

Fig. 2 is a sectional view with the cover in place, taken along the line2--2 of Fig. 1;

Fig. 3 is a view, similar to Fig. l, of an instrument embodying a secondform of the invention, the switch being in elevation;

Fig. 4 is a view, similar to Fig. 3, of an instrument embodying a thirdform of the invention;

Fig. 5 is a sectional view taken along the line 5-5 in Fig. 4;

Fig. 6 is a front elevation of an instrument embodying a fourth form ofthe invention, the cover being omitted;

Fig. 7 is a sectional view taken along the line 1 1 in Fig. 6;

trol the operation of a domestic water supply Fig. 8 is a frontelevation of an instrument embodying a fifth form of the invention, thecover being omitted; and

Fig. 9 is a diagrammatic view illustrating the gap control feature ofthis invention.

All the instruments illustrated in the drawings are of the same generaltype, comprising a casing I5, a Bourdon tube 20, and a switch 25embraced within the arc of the tube 20. The casing l5 comprises a backwall 16 (Fig. 2) side walls l1, and a removable cover It. The Bourdontube 20 is of the usual well known type fixed at its stationary end in asocket 2| in a socket member mounted within the casing I5 and providedat its free end with an adjustable switch-actuating finger 22. Theswitch 25 may be of any desired construction. The switch herein shownfor purposes of illustration is of the kind known as a Mu switch made bythe Mu Switch Corporation, of Boston, Massachusetts. This switchcomprises a pair of spaced contacts 26 and 21, a leaf spring 28 carryingat one end a tip 29 which normally engages the contact 21, a depressiblepin 30 by which the spring 28 may be flexed to bring the tip 29 intoengagement with the contact 26, and an elongate arm 3i flexiblyfulcrummed at one end and with its free 'end portion overlying the tipof the pin 30. A switch of this type is set forth in United StatesPatent No. 1,780,758, dated November 4, 1930. The internal constructionand operation of the switch forms no part of the present invention, itmerely being essential that the switch include a depressible actuatorsuch as the pin 30 and an elongate arm pivoted or flexibly fulcrummed atone end, which like the arm 3| rests against the actuator so that itwill depress the latter in response to pressure applied to the arm.

Figs. 1 and 2 show an instrument wherein the socket 2|, in which thestationary end of the tube 20 is fixed, is provided in a socket member35 which enters the casing I! through an open ing in one side wall andis secured to the back wall it. The forward portion of the socket member35 is cut away and upon it a plate 36 is secured by screws 31 and 33.The screw 31 extends through a hole (not shown) in the plate, and thescrew 38 extends through an arcuate slot 39 in the plate. Thus the screw31 serves as a pivot about which the plate may be swung between thelimits set by the slot 39- being secured in any desired position ofadjustment by the screw 33. The switch 25 is rigidly mounted upon theplate 36 for movement therewith. The finger 22 is preferably of stiillyplyable material and is provided as shown with bends at It and its tipconstiutes a contact element designed to engage that portion of arm itwhich lies to the left of pin 30 (Fig. 1).

The instrument shown in Fig. 3 diii'ers structurally from that justdescribed in that both the screws 45 and 48 by which the plate issecured to the socket member II pass through arcuate slots 41 and 48 sothat the positioning movement of the plate is one of rotation. Thereference characters used in Figs. 1 and 2 are employed in Fig. 3 todesignate common elements of which further description is believedunnecessary.

In the instrument shown in Figs. 4 and 5, the block Ill constituting thesocket member rests upon and is fastened to a T-shaped base iii. A plate52, on which the switch 25 is rigidly mounted, is secured to the basell, so as to extend substantially at right angles to the block 50, byscrews 53 and 54. The screw 54 passes through an arcuate slot II in theplate so that the latter can be adJusted about the screw 53 through anare limited by the slot 55. A set screw 58 carried by a lug I!projecting forwardly from the plate 52 bears against the switch 25 andprovides for accurate adjustment of the plate 52 and switch 25. Thefinger 22 comprises a tongue 58 and a post 69 substantially at rightangles to the tongue and having a ball-shaped tip for contact with armII.

Figs. 6 and 7 illustrate an instrument in which the block or socketmember 80 and the switch 25 are both rigidly secured to a T-shaped base60 mounted on the back wall it of the casing. The switch-actuatingfinger carried by the free end of the Bourdon tube 20 comprises a tongue6! formed with suitable bends 82 and 63 and a set screw 84, the tip ofwhich coacts with the arm 3| of the switch.

In the instrument shown in Fig. 8 the block or socket member 65 passesthrough an opening in a forwardly directed lug 68 forming part of aplate 61 which engages the back wall of the casing and which supportsthe switch 25. The switch-actuating finger carried by the free endvarying the gap between the opening and closing of the switch 28, thatis to say, the pressure differential between the closing and openingpoints. To this end, the finger 22, as above suggested, is preferablystiniy plyable so that it may be bent to vary the location of its tip orcontact element longitudinally of the switch-actuating arm ll.

Fig. 9 is a diagram illustrative of the utility of moving the point ofcontact of the actuator finger 22 longitudinally along the arm II towardor from the switch pin lll. Thus in Fig. ii the arm II isdiagrammatically indicated as a rigid lever fulcrumed at F. The upperend of the switch pin 30 contacts the lever II at the point P and itslower end contacts the switch spring 28 at a point between the fixedsupports (3 and H. The position of the switch spring 28 in cloaof thetube 20 comprises a fiat strip 68 of flexible metal and a set screw 89which is carried by a forwardly directed lug It at the tip of the strip88. the screw 89 engaging the arm 3| of the switch 25.

From the above description of the various embodiments, it will be notedthat in each embodiment the status of the switch 25 is controlled by theBourdon tube 20 which responds in the usual well-known manner to changesin pressure in the system under control, being contracted in radius whenthe pressure drops and expanded when the pressure rises.

Each embodiment includes means by which the relation of the switch 25and the Bourdon tube 20 can be set so that the switch will be closedwhen the pressure in the system has fallen to a predetermined minimum.In the instruments shown in Figs. 1 to 5, inclusive, the switch 25 isrigidly mounted upon a plate which is adjustable within the casing todetermine the initial distance between the tip or contact element of theactuating finger 22 carried by the Bourdon tube 2| and the arm 3| of theswitch. In the instrument shown in Figs. 6 and 7, the set screw 64 whichforms part of the actuating finger 22 can be advanced toward orretracted from the arm SI of the switch, and the same is true of the setscrew ll of the instrument shown in Fig. 8.

Each embodiment also includes means for mg the switch between contacts20 and 2! is indicated in dotted lines, it being noted that to providethe switch-closing flexure of the spring 28 the lower end of the pin I0must move through the vertical distance :r-v. The upper end of the pinmust likewise move through the distance a:u'. Thus the point of contactof the upper end of the pin 30 with the arm II must always move betweenthe points P and P in closing and opening the switch.

It now it be considered that the actuating arm carried by the Bourdontube contacts the lever 3| at the point 22, it will be clear that thispoint must move a distance m-n in order to obtain the necessary actionof the pin ll for closing or opening the switch. On the other hand, ifthe actuator arm carried by the Bourdon tube were so located as tocontact the lever ii at the point 22 then it would be obliged to movethrough the distance m'-n' in closing or opening the switch. and it isclear that the distance m'-n' is greater than the distance m-n inproportion to the distances between the points 22" and 22 and the pointF. Thus, for example, if the distance mn corresponds to a change ofsixteen pounds in the pressure within the Bourdon tube then the distancem'-n' might for example represent a pressure change 01 approximatelytwenty-three pounds. It will thus be clear that by adjusting the finger22 so that its tip engages the arm Ii at different distances from thepoint 'P, the pressure differential through which the switch remainsclosed may be varied at will.

In each embodiment the finger 22 is so formed and of such material thatit can be bent and its outer end moved toward and from the tube into anydesired position, such, for example. as the positions 22- and 22" (Fig.9).

The switch in each embodiment is mounted in the electric controlcircuit, preferably as shown in Fig. 1. The leads 15, 18 from the mainsupply line 17 enter the casing ii through a pipe II and are removablyattached by screws I! to the one end of the switch 25. leads II, IIremovably attached by screws 82 to the other end of the switch 25 passfrom the casing I! through a pipe 8;: taol the diagrammatically shownpump mo- While several embodiments of this invention have been shown anddescribed in detail it will be understood that the invention is notlimited thereto and that other embodiments of the invention may be madewithout departing from the spirit and'scope thereof as set forth in thefollowing claims.

I claim:

1. An instrument of the class described comprising a Bourdon tube, anelectrical switch including a movable elongate actuator, and means fortransmitting movement from the tube to the actuator, saidmotion-transmitting means including a movable contact element supportedby the tip of the tube, said contact element being capable ofindependent adjustment relatively to the actuator in directionstransverse and longitudinally, respectively, of the actuator thereby thecontact element being capable of independent adjustment in directionssubstantially at right angles to each other with reference to theactuator.

3. An instrument of the class described comprising a case, a Bourdontube mounted within said case, a socket in which the stationary end 01'the tube is fixed, a snap switch within the case and including anelongate lever arm which, in response to pressurev variation actuatessaid switch, a plate mounted in said case, means by which said switch isrigidly secured to said plate, and a finger attached to the movable freeend of the tube and adapted in response to the movement of the tube toapply pressure to the arm and thereby actuate the switch, the fingerbeing stiflly pliable thereby to permit it to be bent to vary thedistance between the pressure applying point and the lever fulcrum, theswitch supporting plate being adjustable to vary the initial distancebetween the arm and the finger and thus set the switch for actuation ata predetermined pressure.

4. An instrument of the class described comprising a case, a Bourdontube mounted within said case, means providing a socket in which thestationary end of the tube is fixed, a snap switch within the caseincluding an elongated lever arm which, in response to pressure,actuates said switch, and a finger attached to the movable free end ofthe tube and having a lever contacting element which is adapted inresponse to the movement of the tube to apply pressure to the arm andthereby actuate the switch, the contact element of the finger beingadjustable toward and from the lever arm thereby to determine thepressure at which contact is initially made, the finger being soconstructed and arranged that the contact element is movable relative tothe lever arm in a direction longitudinally of the latter thereby tovary the point at which the contact element engages the arm and thusdetermine the pressure differential between the closing and opening ofthe switch.

5. An instrument of the class described comprising a case. a Bourdontube mounted within said case, means providing a socket in which thestationary end or the tube is fixed, a snap switch within the case andincluding an elongate lever arm which in response to pressure actuatessaid switch, a plate mounted in said case, means by which said switch isrigidly secured to said plate and a finger attached to the movable ireeend of the tube and adapted in response to the movement of the tube toapply pressure to the arm and actuate the switch, the switch supportingplate being adjustable to vary the distance between the arm and thefinger and thus set the switch for actuation at a predeterminedpressure, and the finger being movable longitudinally of the arin tovary the point at which it contacts with the arm and thereby topredeterinine the pressure diiferential between closing and opening ofthe switch.

6. An instrument of the class described comprising a case, a Bourdontube mounted within said case, means providing a socket in which thestationary end of the tube is fixed, a snap switch within the case, theswitch including a depressible pin by which the switch contacts areclosed, an

.elongate movable lever arm which rests upon one end of the pin andwhich, in response to pressure applied thereto, depresses the pin toclose the switch contacts, and a finger attached to the movable free endof the tube and having a tip which is adapted to bear upon the arm andapply pressure thereto as the tube moves in one direction said fingerbeing of stifiiy pliable material whereby it may be bent to shift itstip longitudinally of the lever arm.

7. An instrument of the class described comprising a case, a Bourdontube mounted within said case, means providing a socket in which thestationary end of the tube is fixed, a snap switch within the case, theswitch including a depressible pin by which the switch contacts areclosed and an elongate lever arm which rests upon one end of the pin andwhich, in response to pressure applied thereto, depresses the pin toclose the switch contacts, and an actuating finger attached to themovable free end of the tube and adapted to bear upon the arm and applypressure thereto as the tube moves in one direction, the finger beingadjustable to vary the point, longitudinally of the arm, at which itcontacts the arm thereby to determine the range of pressure betweenclosing and opening the switch. 7

8. An instrument of the class described comprising a Bourdon tube, anelectrical switch including a movable actuator, and means fortransmitting movement from the tube to the actuator, saidmotion-transmitting means including a finger fixed at one end to thetubetip and having a contact element at its other end engageable withthe actuator, said finger being stifliy pliable thereby to permit theinitial position of the contact element relative to the actuator to bevaried.

9. An instrument of the class described comprising a Bourdon tube, anelectrical switch including a movable actuator, and means fortransmitting movement from the tube to the actuator, saidmotion-transmitting means including a finger fixed at one end to thetube tip, said finger having a screw-threaded aperture near its otherend and an adjustable screw disposed in said aperture and constituting acontact element for engagement with the actuator, the axial adjustmentoi the screw being eil'ective to determine the initial pressure at whichthe switch shall close, the finger being stimy pliable whereby thecontact screw may be moved bodily in a direction substantiallyperpendicular to its axis thereby to determine the range of pressurewithin which the switch will remain closed.

FRANK H. HOPKINS.

